Integrated circuits for driving systems through half-bridge power stages are widely used in industrial applications, such as for driving three-phase motors, stepper motors, brushless motors or a generic resistance-inductance (R-L) actuator. When these integrated devices possess only one logic command input, it becomes necessary to implement a circuit that regulates the switching dead-time to avoid a simultaneous state of conduction of the two branches, that is, of the two power devices (HIGH SIDE and LOW SIDE) of the half-bridge stage. In the majority of cases, it is necessary to program or adjust the value of the switching dead-time by taking into account the electrical characteristics of the driven R-L actuator.
FIG. 1 shows a classical way of realizing such a dead-time programming function, using a dedicated PIN of the integrated device IC1. This dedicated pin serves to implement both the programming function of the switching dead-time by suitably dimensioning the external resistor R.sub.ex, and the disabling/enabling logic function of the half-bridge power stage of the integrated device through a dedicated external switch S1, controlled by a specific logic command SHUTDOWN.
By referring to the conventional scheme of FIG. 1, the amplifier (buffer) A1 restores a certain reference voltage Vbg (typically a band-gap voltage) on the dedicated PIN. Through the external resistor R.sub.ex it is then possible to regulate the switching dead-time (Tdt) generated by the DEAD-TIME block, by considering that: ##EQU1## where C is the delay capacitance within the DEAD-TIME circuit block, V is the voltage existing on such capacitance C at the switching instant, and I.sub.R is the current that charges the capacitance C.
The comparator COMP1 compares the voltage on the dedicated pin with ceratin reference voltage REF1, and produces a shutdown or enabling signal of the output power stage HALF-BRIDGE. In practice, the logic function of "shutdown" is implemented by forcing a low logic stage on the pin PIN as referred to the threshold REF1 established on the inverting input node of COMP1.
According to this typical circuit implementation of a programming function of the switching dead-time and an enabling/disabling function of the half-bridge power stage, the output impedance of the operational amplifier (buffer) A1 is necessarily low to allow a good degree of precision for the circuit, as well as immunity to noise. These characteristics of known circuits do not allow connecting in common all the respective dedicated pins (PIN) and the use of a unique set of external components to implement the programming function of the switching dead-time and of enabling/disabling of all the integrated power devices of the multi-phase driving system. This is so especially when they include several output stages, as in the case for driving multi-phase motors. In practice, according to the prior art, it is necessary to duplicate the external components and the respective lines for each integrated device (IC1, IC2, IC3), as depicted in FIG. 2.